Introduction

The Asus DSL-N55U is a router intended for use with ADSL and ADSL2+ services
and includes an ADSL modem, rather than the Ethernet WAN port of the very
similar RT-N66U router we have also reviewed. The similarity between the two
routers extends beyond the black design with the web interface offering almost
identical functionality.

The main points on the feature list for the DSL-N55U are:

Built in ASDL2+ modem

Four Gigabit Ethernet ports

Three detachable wireless antenna

Two USB sockets

Dual band 2.4GHz and 5GHz a/b/g/n wireless networks

Support for IPv6

Quality of Service controls

Media server with support for DLNA, iTunes, FTP, HTTP

USB Printer sharing ports

3G/4G dongle backup connection support

Built in VPN Server

Wireless Guest Network support

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The 750 Mbps wireless speeds are though the theoretical combination of 300
Mbps (150 Mbps in any single direction) from the 2.4GHz band, and 300 Mbps (150
Mbps in one direction) on the 5GHz band. This is many times faster than ADSL2+
can manage at a maximum of 24 Mbps, but with the media server functionality,
buyers of this router are likely to be moving a lot of local LAN traffic around
also. The inclusion of two CPU in the device should help avoid heavy LAN
traffic impacting on the ability for the router to handle the ADSL/ADSL2+
signals.

This review has been carried out with firmware version 3.0.0.4.188 and ADSL
driver version 3.16.18.0. Running on both a Sky ADSL2+ service, and a BT
Wholesale based ADSL2+ service.

What you get for your
money

The router retails for around £90 to £100 (October 2012), and the retail box
contains the items below.

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Power supply, with interchangeable UK and EU prongs. 19V 1.58A output

3 detachable antennas

ADSL microfilter

Ethernet cable

RJ11 modem lead

Router

An unusual inclusion is the flat profile Ethernet cable. There is a paper
manual and the usual leaflets, but unless this is your very first router there
is very little to be learnt from this paperwork.

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Router manufacturers have largely learnt to include the basic access details
for the device on the underside, they also include a reminder to change the
routers default username and password of admin. There are two wall mounting
screws, but no stand like the RT- N66U.

The power supply (19v, 1.58A output) follows the normal Asus pattern of
having a blue LED in it, and the array of LED on the front of the router are
bright blue. While LED feedback is very useful the brightness of the Asus LEDs
is a bit too much, but then nothing some black tape will not fix.

There is a CD supplied which you can use to configure the router, but this
does not work for Mac users, so we will avoid using the CD in this guide.

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The rear of the router is pretty crowded- perhaps a future design might
consider moving the USB ports to the side of the router so that it is less
cluttered. The inclusion of a small slider switch to turn off the wireless side
of the router is a good addition, though its location next to the power rocker
switch means you need to look rather than just fumble behind the router.

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The nine LED’s on the front of the case usefully include one LED to show
when the modem has synchronised to the DSLAM/MSAN in the telephone exchange,
and a different LED to show Internet connectivity (this lights up when you have
been authenticated with your broadband provider).

The separate 2.4GHz and 5GHz LED’s are useful as you can individually
disable these networks via the web interface, and in crowded WiFi areas it
would be polite if all your devices support 5GHz to turn off the 2.4GHz
signal.

Configuring the DSL-N55U

The router holds your hand nicely when you first connect to it. Ideally we
recommend when setting up any broadband hardware to use an Ethernet connection
if possible, but the DSL-N55U like many is happy if you use its wireless
connection. The default security details are on the label under the router.

As with other Asus networking hardware it does a redirect to the
configuration page as soon as you open the web browser, negating the need to
know the routers default IP address of 192.168.1.1 or that it can be accessed
by the domain name www.asusnetwork.net

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The first step is to configure an administrator password (which is forced by
the router), which is a nice step to ensure people do not leave a device on its
default settings. While a good idea, there has been little thought put into
restrictions, so you can actually set an insecure password that is a single
space character.

One other oddity that is common with the Asus RT-N66U is that the
stylesheets for the web interface can result in odd looking displays when using
Internet Explorer 9. This problem is minor and just means you need to pick a
reasonable page size when using Internet Explorer to configure the router.

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The router firmware has a list of commonly used settings for around the
world, and while it is not a complete list of the UK market, the major options
are covered. We did try the Sky MER option but were unable to get it to work,
but the Sky LLU line we did try the router on was happy using PPPoA. We elected
to use the not listed option for the screenshots in this review.

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The router offers PPPoE, PPPoA, MER, Bridge and IPoA options for the
authentication protocol. The bulk of this review was done using a BT Wholesale
ADSL2+ based service, we also successfully used the router with a Sky LLU
service. The settings for a generic BT Wholesale ADSL or ADSL2+ service are VPI
0, VCI 38, Protocol PPPoA, Encapsulation Mode VC/MUX. The next step is to enter
the username and password for your broadband connection as supplied by your
broadband provider.

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Following the pattern of forcing you to alter the default security settings
the next stage of configuration is to specify the security settings for your
wireless network. If you wish you can skip this stage, but setting your own
strong security key for the wireless encryption is recommended. This is the
last stage in the configuration; once the settings are saved you are presented
with a summary page letting you do a final double check of all the settings.
Once you have confirmed all the settings we arrive at the familiar Asus router
home page.

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The similarity with the RT-N66U interface means that many features are
identical, so we will try and concentrate on the differences. Once the ADSL
service is up and running the first port of call for any new hardware is to see
what speed the device has connected at, and for the DSL-N55U this is hidden
away down in the System Log.

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Compared to other features like the traffic manager the interface is
relatively crude, but the critical data is displayed, namely the connection
speed (Data Rate Up/Down), attenuation and noise margin figures. The
performance of the router in terms of ADSL2+ connection is on a par with other
good routers.

Using DSL-N55U with Sky ADSL2+ Broadband
Service

The Sky ADSL2+ service comes supplied with a router, but both the old Sagem
2504n and the newer SR101 lack the extra wireless features and media server
functionality that third party routers can offer.

For Sky customers, while the service requires you to use the supplied
router, generally so long as you double check any fault conditions are
identical with their supplied router there is little to stop you using your own
router. Sky does not normally supply the username and password for the service,
but there are several websites where given the MAC address of the supplied
routers LAN interface and default wireless key you can obtain the actual
username and password.

We duplicated the configuration of the Sky router settings, which on our LLU
line were PPPoA, with the standard VPI/VCI of 0/38 and VCMux encapsulation.
This did not work, but once we copied the WAN ports MAC from the old Sky
router, the DSL-N55U connected to the Sky service with no problems.

Some Sky LLU connections use MER authentication, but we were unable to test
this, as the Sky hardware in our local exchange appears to only use PPPoA.

IPv6 Connectivity

The router has support for IPv6 built in, and thus it would be remiss of us
to not try and use it. All we can say is that we tried and failed to get IP v6
operating with the router. With other devices it is a pretty simple task of
just enabling IPv6 on the WAN interface, but the DSL-N55U has so many options
it is clear that the system is not ready for mass market use in that
respect.

Traffic Manager and
QoS

One of the problems on the sort of ADSL and ADSL2+ connections the router
supports is managing the conflicts that arise when one person in a home wants
to do something like online gaming which is very latency sensitive while
someone else is downloading a large software update. The DSL-N55U provides the
router administrator several options to avoid the conflicts that can arise from
this conundrum.

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By default QoS is turned off, so we have turned it on, and fed in our
approximate upload and download bandwidth figures. This is the QoS at its
simplest level and will rely on a set of automatic rules. For more complicated
scenarios you can switch to two manual modes, setting priority rules or full
QoS controls.

The default rules are not perfect as we find that if we watched a 1080p
YouTube clip, pings still increased from a standard 16 ms to around 80 ms.
Though as the configuration page states the rules are setup to really ensure
that P2P applications do not adversely impact on web surfing and gaming. So now
let us see if we can configure the system to let High Definition YouTube videos
still play, but not affect latency.

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A little bit of experimenting later and we arrived at the above set of
rules, which reserve up to 650 Kbps of our connection for things like ICMP
packets, and allowed YouTube streaming which we found via a process of
elimination is considered Low priority traffic by the router. 3.87 Mbps is
usually just enough capacity to avoid buffering of a 1080p stream. Other
streaming services will use different bit-rates, so you will need to experiment
also, but we know at least the system works, creating a starting point to build
custom rules.

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The above screenshot shows the data coming across the broadband connection
when we had implemented our custom rules. Without the QoS rules we had setup, a
1080p clip would normally use bandwidth in the pattern below. The first major
peak is actually a thinkbroadband speedtest, followed by the blue which is the
colour used to show upstream data. The regular spikes show the YouTube video
playing fetching data in batches, which results in spiky latency for other
users on this 6.5 Mbps connection.

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The Traffic Manager screenshots show it running in Real-Time mode, but you
can switch to a day view which displays the last 24 hours of traffic or you can
display the last 30 days of data. The ability to switch between Internet,
Ethernet and the two wireless bands is useful when tracking down where your
Internet bandwidth is vanishing. The other way to manage Quality of Service is
to use the user-defined QoS rules. We have played around to setup a scenario
where anyone using BitTorrent will see their speeds limited to 50 Kilo
Bytes/second if other traffic needs capacity. These rules also allow you to set
different priorities based on the IP address of the client, thus if you pay the
bill you could set the rules up so that you got the largest share of the
connection when it was busy.

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The list of services does not cover every possible permutation, but it is
easy enough to add a manual rule, by specifying the source IP/MAC, port,
protocol and transfer limits and clicking the ADD(+) button . Port ranges are
easily specified e.g. 400:800 covers all ports from 400 through to 800, or if
you want to lock down every port <65535 can be used.

USB Applications and
Media Server

One of the major features of the DSL-N55U is the two USB ports that allow
you to attach various USB storage devices, or just simply charge your mobile
phone with a USB charging lead.

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There are some differences compared to the RT-N66U Ethernet router, the
Download Master software has been replaced by Media Server software, and the
interface makes it clear that 4G USB dongles are supported.

AiDisk and Servers Center

This is identical to the Asus RT-N66U and allows you to configure how data
on a USB storage device is shared, including allowing you to make the data
available over the Internet. The same dynamic DNS services are supported, so
that users on ADSL2+ connections with dynamic IP addresses are not
disadvantaged.

Network Printer Server

If you own a USB printer that does not have built-in wireless or an Ethernet
port to allow sharing on your home network, you can connect it to a USB port on
the DSL-N55U and use either the Asus EZ printer software or the LPR protocol to
share the printer between the computers on your network via the router.

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Media Server

If you have a USB storage device installed you can copy onto it the Media
Server software which the router will download from Asus.

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Installing the software takes around a minute to reach the 99% complete
figure, and then seems to sit and wait for a long time, we presume this delay
is because it is indexing the USB storage device. So do wait for the
installation to complete and be returned to the main USB Application web
page.

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With the software installed you gain the ability to control the options such
as the DNLA Media Server that allows you to serve media from the USB device to
any DNLA compliant player on your network. Or for those that make extensive use
of iTunes, they may want to enable the iTunes server which can act as a
repository on your LAN that all your iTunes software can access. The ability to
download files using the router directly onto the USB storage device is one
major feature missing from the DSL-N55U USB functionality.

Wireless
Configuration

The router supports simultaneous use of 2.4GHz (b/g/n) and 5GHz (a/n)
wireless networks, and you can configure each independently, restricting your
use on the lower band to the slower 20 MHz band to be kinder to other wireless
networks in the area, and using the faster 40 MHz band only on the 5GHz
band.

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The back of the router does have a switch allowing you to physically switch
off the wireless network, which will save a small amount of power; if you want
to disable just one of the bands you need to switch to the professional setting
tab.

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To disable the 5GHz band, simply untick the seven check boxes that control
when the wireless network is enabled.

VPN Server – Connecting remotely
to your home network

The VPN server allows you to configure a username and password that allows
someone with a PPTP VPN client to connect to your home network across the
Internet.

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We have added a user called review with the very insecure password of
review, do remember to actually enable the PPTP Server option, as this led to
some head scratching initially until we realised we had missed that important
step. The more complex details of the VPN are under the VPN Details tab. We
have left them at their defaults for the review to keep life simple. Once the
settings have been applied, anyone who knows your WAN IP address they should be
able to setup a VPN client to connect to the router over the Internet. We then,
using a different Internet connection, setup the VPN client in Windows 7.

Screenshots for creating VPN Connection with Microsoft Windows
7Click on an image to see it in full resolution.

Windows 7 will cycle through various VPN configuration options until it
finds the one that matches the server. To speed this up you can alter the
properties to restrict the connection to PPTP only. Once connected, you should
see the VPN appear in your Network and Sharing Center if using Windows.

The VPN Server does not set a gateway address, so any Internet access will
still occur via your primary Internet connection. The VPN allows you access to
all network resources on your home network. This is not restricted to file
shares, you could connect to the VPN to then gain access to remote desktop on a
computer, with the VPN providing an extra layer of security that would not be
present if you relied on simple port forwarding rules.

Firewall

The firewall configuration is the same as the Asus RT-N66U, and beyond the
basics of a simple DoS protection system, and the ability to allow ping
requests so that tools like our Broadband Quality Monitor will work, the main
use of the firewall will be its ability block certain applications from
accessing the Internet either completely or based upon a time system.

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To illustrate what you can do with the Network Services Filter, we have
setup a blocking rule that should block all Internet access for the computer
using the IP address 192.168.1.2 between the hours of 9pm to 9am during the
week, and 11pm to 9am at the weekend.

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The filter table type allows you to switch to a white list approach, where
everything is blocked apart from the specified services. The filter table does
provide notes to explain what syntax is allowed for port ranges, but unlike the
QoS rules there is no option to filter based on MAC of a particular
machine.

WAN Configuration
Options, Virtual Server and DMZ

The WAN settings follow the same pattern as the RT-N66U, the main difference
is the ability to edit the ADSL connection parameters. The page is pretty long
so those who find the need to tweak the router based MTU will need to scroll
down, a maximum value of 1492 can be set.

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The inclusion of DDNS functionality will be welcomed by those people on
providers with dynamic IP addresses, and supports both Asus own service and
services from dyndns.org, tzo.com, zoneedit.com, dnsomatic.net,
tunnelbroker.net and no-ip.com.

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The port forwarding allows people running servers to forward the selected
TCP or UDP ports to the appropriate machine on their LAN. The local IP field
offers a list of the machines that can be seen by the router, or you can
manually specify an IP address. Port ranges are supported e.g. 110:130 covers
the range 110 through to 130. The famous server and game lists provide settings
for the most common applications, and while Xbox Live was listed we found no
need to forward any ports to get Xbox Live to work with the router, though if
you elect to disable UPnP the situation may well be different.

Administration

DSL Settings

The router allows you to force the ADSL mode, picking whether to use ADSL
(G.DMT), ADSL2 and ADSL2+ which can be useful if your telephone line is proving
to be slightly unstable, as ADSL and ADSL2 modes can for some telephone lines
be more stable than ADSL2+.

Save/Restore Router Settings

With the wide range of settings on the router, the ability to backup the
settings from the router is very useful. For example once you have got the
router working you can backup the config to a file on your computer, and then
if you get carried away when playing with the QoS or firewall sections you can
quickly restore the router to your original working configuration.

System Logs

The system logs are pretty comprehensive, and in many cases will overwhelm
the normal user.

General Log: General router messages. The file can be saved to disk and be
opened using apps like WordPad and TextPad.

DHCP Leases: A log of all the DHCP IP addresses handed out since the last
reboot.

Wireless Log: The details of which wireless channels the router is
using.

Port Forwarding: Very useful to look to see what ports UPnP is using on
your network.

Routing Table: The routing rules the router is using, and provides a wealth
of IPv6 information.

ADSL Log: Only provides the current ADSL connection parameters.

Performance

The router in daily use performs very well, and one of the lines used during
the review does stress some routers when it is dark and the noise floor rises,
which can result in some twitchy modems rebooting several times in an evening.
The CPU in the router appears to be up to the task too, as there was not the
usual lag in the web interface when playing around with the 3G USB backup
modem.

In terms of its ADSL2+ abilities, and how fast the modem pushes the line, it
was on par with the Billion 7800N and AVM Fritzbox 7390 in this respect. There
is not all the tweakability of these other routers, but the price is a fair bit
lower which makes up for this.

A dual band router may seem overkill when the fastest Internet connection
supported is 24 Mbps, but with the increasing amount of people running media
servers on their LAN, and the presence of one built into the router, the local
wireless speed becomes more important.

We tested each wireless band independently, but as they are proper dual
bands you can be serving media at full speed on 2.4GHz band, and still have
another band able to stream HD material without breaking a sweat.

Our testing setup is our usual one, which makes it easy to compare the
results from our various reviews. For those looking to see how the router
performs with respect to walls, the testing in the kitchen and conservatory
show how the router performs when the signal has to go diagonally through a
couple of walls. The measured speed is actually an average measured across a
period of 30 seconds.

2.4GHz Wireless Performance

Location

Nominal Link Speed

Measured Speed

Top Floor - Same room

270 Mbps

82 Mbps

Middle Floor

270 Mbps

65 Mbps

Ground Floor

243 Mbps

38 Mbps

Kitchen

90 Mbps

17 Mbps

Conservatory

1 Mbps

0.1 Mbps

Shed

2 Mbps

0.8 Mbps

5GHz Wireless Performance

Location

Nominal Link Speed

Measured Speed

Top Floor - Same room

300 Mbps

96 Mbps

Middle Floor

364 Mbps

78 Mbps

Ground Floor

324 Mbps

73 Mbps

Kitchen

80 Mbps

22 Mbps

Conservatory

No Signal

No Signal

Shed

No Signal

No Signal

The coverage is pretty much always worse with the 5GHz band on all routers,
because the 5GHz is attenuated by building materials more easily, reducing the
distance the signal will travel. The range of the 2.4GHz was a little
disappointing as we have had better coverage with other devices at the
shed.

Conclusions

The DSL-N55U with a retail price in the range £80 to 90 is not the cheapest
ADSL2+ modem/router by a long way, and lacks some of the bells and whistles of
the more expensive models, but does pack a good performance for its price.

The price point means that you really should be sure of wanting to use the
media server or the extensive QoS functionality of the router to make it worth
buying. If Asus can add the Download Master functionality that its Ethernet
routers support then the router would be even more desirable.